OSGi Aware Programming in Tuscany (TUSCANY) edited by Luciano Resende
Page:
http://cwiki.apache.org/confluence/display/TUSCANY/OSGi+Aware+Programming+in+Tuscany
Changes:
http://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=101617&originalVersion=2&revisedVersion=3
Content:
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h2.Motivation for OSGi
The Apache Tuscany project has become a large project, with various
extensions and component types that brings to the SCA Runtime different levels
of dependencies. With its growth, Tuscany also started to have it's SPIs
violated by some of these extensions, and some of the boundaries between
sub-systems are broken, as there wasn't any enforcement of these boundaries.
The OSGi model provides a very powerful and flexible framework to develop
applications in a modular fashion with a high degree of control over
classloading inter-dependencies over modules. An OSGi module (a.k.a bundle)
have a manifest file (META-INF\manifest.mf) that contains module information
such as "name", "version" and also a list of what packages are being exported,
and what packages are being imported from the given bundle, providing ways to
easily enforce module boundaries.
h2.Tuscany and OSGi - 3rd party dependencies
Currently we are wrapping the 3rd party dependencies as OSGi bundles, but
leaving it unpacked (a.k.a folder structure). This allow use to use the same
dependency jars in a OSGi environment as well as in a non-OSGI environment and
generating no side effect on our distribution footprint.
!osgi_3rd_party_dependencies.JPG!
h2.Tuscany and OSGi - Granularity
The granularity used to define modules should be very familiar to all
tuscany developers,
Tuscany Modules --> OSGi Bundles
3rd Party Libraries --> OSGi Bundles (using unpacked wrap style bundle)
h2.Properly defining new Tuscany modules as an OSGi bundle
When adding new modules to the Tuscany project, the developer will need to
create the OSGi Manifest to properly describe the new module as an OSGi bundle.
These artifacts can be automatically generated using the Felix
maven-bundle-plugin and should be available from svn repository once it's
stable.
h4.Generating OSGi manifest with Felix maven-bundle-plugin
{code:title="configuring maven to generate the OSGi manifest"}
<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<configuration>
<instructions>
<!-- Bundle versioned from Tuscany version -->
<Bundle-Version>${tuscany.version}</Bundle-Version>
<!-- Bundle Symbolic name -->
<Bundle-SymbolicName>org.apache.tuscany.sca.api</Bundle-SymbolicName>
<!-- Bundle description from pom description -->
<Bundle-Description>${pom.description}</Bundle-Description>
<!-- Export org.osoa.sca and all sub-packages -->
<Export-Package>org.osoa.sca*</Export-Package>
<!-- No Import-Package so calculate imports from code dependencies
-->
</instructions>
</configuration>
</plugin>
{code}
Below is a manifest that was generated for one of the Tuscany modules using the
felix maven-bundle-plugin.
{code:title="OSGi Manifest (META-INF\manifest.mf"}
Manifest-Version: 1.0
Export-Package: org.apache.tuscany.sca.assembly;uses:="javax.xml.xpath
,org.apache.tuscany.sca.assembly.impl,org.apache.tuscany.sca.policy,o
rg.apache.tuscany.sca.interfacedef,javax.xml.namespace";version="1.4"
,org.apache.tuscany.sca.assembly.impl;uses:="javax.xml.xpath,org.apac
he.tuscany.sca.assembly,org.apache.tuscany.sca.policy,org.apache.tusc
any.sca.interfacedef,javax.xml.namespace";version="1.4",org.apache.tu
scany.sca.assembly.builder;uses:="org.apache.tuscany.sca.assembly,org
.apache.tuscany.sca.definitions,org.apache.tuscany.sca.core,org.apach
e.tuscany.sca.monitor,org.apache.tuscany.sca.interfacedef,org.apache.
tuscany.sca.extensibility";version="1.4"
Private-Package: org.apache.tuscany.sca.assembly.builder.impl;version=
"1.4"
Tool: Bnd-0.0.255
Bundle-Name: Apache Tuscany SCA Assembly Model
Created-By: 1.6.0_07 (Sun Microsystems Inc.)
Bundle-Vendor: The Apache Software Foundation
Bundle-Version: 1.4
Bnd-LastModified: 1225397097203
Bundle-ManifestVersion: 2
Bundle-License: http://www.apache.org/licenses/LICENSE-2.0.txt
Bundle-Description: Apache Tuscany SCA Assembly Model
Import-Package: javax.xml.namespace,javax.xml.parsers,javax.xml.transf
orm,javax.xml.transform.dom,javax.xml.transform.sax,javax.xml.xpath,o
rg.apache.tuscany.sca.assembly;version="1.4",org.apache.tuscany.sca.a
ssembly.builder;version="1.4",org.apache.tuscany.sca.assembly.impl;ve
rsion="1.4",org.apache.tuscany.sca.core;version="1.4",org.apache.tusc
any.sca.definitions;version="1.4",org.apache.tuscany.sca.extensibilit
y;version="1.4",org.apache.tuscany.sca.interfacedef;version="1.4",org
.apache.tuscany.sca.monitor;version="1.4",org.apache.tuscany.sca.poli
cy;version="1.4",org.apache.tuscany.sca.policy.util;version="1.4",org
.w3c.dom,org.xml.sax,junit.framework;resolution:=optional,org.apache.
tuscany.sca.interfacedef.impl;version="1.4";resolution:=optional,org.
junit;resolution:=optional
Bundle-SymbolicName: org.apache.tuscany.sca.assembly
Bundle-DocURL: http://www.apache.org/
{code}
h2.Tweaking the OSGi manifest
Eclipse PDE provides good tooling for editing and maintaining OSGi manifest
files.
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